Process and composition for carroting furs



Patented May 20, 1941 STATES Jacob Dolid, Bridgeport, Conn.

No Drawing.

Application June 27, 1940,

.Serial No. 342,764

13 Claims.

This invention relates to the art of treating fur and like fibers to give them tight felting properties and to a nonmercuric composition of matter adapted to impart such properties to the fur or the like fibers when treated therewith. The present application is a continuation in part of my previous application Serial- No. 276,834, filed June 1, 1939.

The treatment of fur and like fibers to give them felting properties, that is, so that fur cut from pelts will felt and shrink properly, the initial steps of forming feltbodies, has been termed carroting, Carroting is a process of chemically treating fur or the like to impart thereto the requisite felting properties and is dependent on the action of the chemical reagents of the carroting solution which removes fats and other foreign substances, as well as reacts with the proteins of the fur or the like.

It is well known that a certain carroting effect is produced by the action of strong acids on the fur, such as sulphuric acid, which produces only a hydrolyzing action. The carroting effect of such acids which is relatively weak when they are alone is greatly increased when the carroting is accomplished in the presence of an oxidizing agent. Accordingly, it is generally accepted now that the carroting process, in its most effective form, involves a hydrolyzing action by the acid on the animal fibers, and an oxidizing action by an oxidizing agent present in the solution.

The carro treatment heretofore most commonly used 12 been the application to the fur of an aquec..s carroting solution comprising mercuric nitrate and nitric acid, which as is well known is an oxidizing agent. In this treatment, the nitric acid apparently acts simultaneously as a hydrolyzing and an oxidizing agent, producing a hydrolyzing and oxidizing reaction on the animal fibers. The function of the mercury in this solution at least in part appears to be the inhibition and control of the destructive action of the nitric acid. This inhibiting and controlling effect seems to be accomplished as a result of the formation by the mercury of insoluble or unreactive compounds with the hydrolytic products of the proteins of the fur fibers.

Although from a purely chemical viewpoint,

this carroting solution reacts with the fur fiber to transform-the same into a form which felts readily, it is, nevertheless objectionable from a social standpoint in that mercury is poisonous and its presence in the solution, as well as in fur treated therewith, is a constant source of danger to the workers in the industry. The use of this carroting solution and the resultant impairment to the health of the workers has become avery serious problem to the industry.

It has been proposed to use carroting solutions containing as oxidizing agents, oxygen-liberating agents such as hydrogen peroxide or per-salts such as'perborates, percarbonates, persulfates, or the like. The said per-salts generally liberate hydrogen peroxide, especially in the presence of acids, in the carroting solution. Such oxygenliberating agents are relatively unstable, since hydrogen peroxide decomposes readily, liberating molecular oxygen, and its decomposition is vastly accelerated by catalytic impurities which are introduced into the carroting solution du ing use. As a result, the strength of such carroting solutions changes during use, resulting in uneven carroting of fur treated therewith. Furthermore, it has been found that fur carroted with relatively unstable oxygen-liberating agents of the aforesaid type, and especially with hydrogen peroxide, gradually loses its felting properties during storage and is therefore unsuitable if it is desired to store the fur for any material length of time. This effect is a material disadvantage in practice.

Thepresent invention comprises a carroting solution which produces the fundamental hydrolyzing and oxidizing reactions necessary to carrot the fur and yet insofar as is known now is nonpoisonous. Furthermore, the carroting solution of the present invention is stable, retaining its full strength practically unchanged during use whereby fur treated therewith is uniformly car- 'roted. Moreover, fur carroted with the present carroting solution retains its felting properties unchanged during storage. 1 a

The carroting solution of my invention contains a permolybdate,.that is, a permolybdic acid or salts thereof, preferably in combination with mineral or other acids or their salts, but is sub-.

stantially free from oxygen-liberating agents, i. e. oxidizing agents which are capable of yielding atomic oxygen to the fur, which are less stable than permolybdates. The term, permolybdate, is intended to designate permonomolybdic acid (HzMOOs), perdimolybdic acid (HzMoOs), and their salts, and permolybdic acid refers to either or both of the aforesaid acids.

Permolybdates are distinguished from oxygenliberating agents such as hydrogen peroxide, perborates, percarbonates and the like by their comparatively high stability. For instance, it is possible to boil an aqueous solution of permolybdates without material decomposition thereof,

compounds are completely decomposed thereby.

In my preferred carroting solution, the permolybdic acid acts as an oxidizing agent while the mineral or other acid acts as a hydrolyzing agent, so that both hydrolysis and oxidation, which appear to be the important reactions involved in transforming the fur fiber into a form which felts readily, are eflected.

As a result of the stability of the permolybdates, and the substantial absence of comparatively unstable oxygen-liberating agents such as hydrogen peroxide, perborates, etc., in my carroting solutions, the carroted fur produced by treatment therewith retains its felting properties 1mchanged during storage, and the carroting solu- 2,242,688 while hydrogen peroxide and the aforesaid per-.

. if present together with permolybdates, exert a tion retains its full strength during use, whereby fur treated therewith is uniformly carroted.

Furthermore, I have found that, in addition to acting as an oxidizing agent, permolybdate radicals, or the molybdenum compounds resulting from their reduction apparently combine with the hydrolytic products of the fiber protein to form insoluble compounds, thus inhibiting and controlling any destructive actions which might result from excessive hydrolysis and oxidation.

The tendency of permolyodate radicals or the molybdenum compounds resulting from their reduotion to combine with the partially decomposed fur proteins is even more pronounced in the case of combinations of the permolybdate radical with borates, especially in acid solution. Permolybdic acids are quite soluble in water, in contrast with molybdic acid.

It will be seen, therefore, that permolybdic acids or the molybdenum compounds resulting from their reduction can be said to replace the function at least in part of the mercury in the heretofore proposed mercurial carroting solutions.

The carroting solution of my invention may be prepared in numerous ways. While it is possible to obtain permolybdic acids or their salts in the solid form, and-to add them to the aqueous carroting solution, it is generally more convenient to prepare a solution of molybdic acid or a molybdate, and to oxidize it in solution, for instance by means of hydrogen peroxide or a perborate, to a permoiybd ic acid or a permolybdate. Molybdic acid, for instance, while capable of forming complex compounds, may be considered present as H2MoO4. Dependingupon the degree of oxidation, the latter may be partially or completely converted to permon-omolybdic acid. The latter may be partially or completely converted to perdimolybdic acid. This range of oxidizability, it

carroting action upon the fur independently of the molybdenum compounds, and thus, by avoiding their presence in the carroting solution of the present invention the disadvantageous efiects upon the fur, resulting therefrom as hereinbefore discussed, are avoided.

Permolybdic' acids alone give very definite carroting effects, but I have found that the effect is increased by the presence of a mineral or other acid, or alkali metal or ammonium salts thereof, in the carroting solution. Thus, a convenient method for preparing the carroting solutions of the present invention comprises dissolving molybdenum 'trioxide in aqua ammonia to form a solution of ammonium molybdate, acidifying the solution by means of a suitable acid such as nitric acid, for instance by adding suflicient nitric acid to combine with all of the ammonium radicals or an excess thereof, and subsequently oxidizing the molybdic acid liberated thereby by adding a, quantity of hydrogen peroxide or sodium perborate in an amount not greater than that required to oxidize all of the molybdic acid to perdimolybdic acid.

tion of the nitric acid with ammonium molybdate places ammonium nitrate in the carroting solution, and with sodium perborate results in the formation of sodium nitrate. Reduction of the perborate by the molybdate, which as hereinbefore set forth is substantially complete, places the borate radical in the solution, and if an excess of nitric acid is present, boric acid is formed.

The following examples, weight, illustrate the carroting solutions and procedure of the present invention. The examples are purely illustrative and as various modifications thereof may be made, I do not wish to be limited thereby.

Example 1 10 parts of molybdenum trioxide (M003), 85% pure, are disolved in 12 parts of aqua ammonia. having a density of 28 B., diluted with 40 parts water;- Thesolution is acidified by adding 57' .parts of nitric acid having a. density of 40 B.,

The perborate is substantially completely reduced will be seen, affords a convenient means for con-- trolling the oxidizing power of the carroting solution. A

When relatively unstable oxygen-liberating agents such as hydrogen peroxide or perborates are used to oxidize the molybdic acid or molybdate to a permolybdate, the said reagents are preferably used in an amount not greater than that required to oxidize all of the molybdate to a perdimolybdate, in order to avoid the presence of any substantial quantity of such relatively unstable oxygen-liberating agents in the carroting solution. Hydrogen peroxide is thus substantially completely reduced in the said reaction to water, while perborates are substantially completely reduced to borates. If an excess of such agents is used, it is destroyed, for instance by boiling, be-

. fore the solution is used for carroting. Namely,

tda'borate, and since the nitric acid which is added is in excess of the sodium and ammonium ions, vboric acid is liberated and the solution contains sodium and ammonium nitrates in addition to the exams nitric acid.

Example 2 A solutiorrof ammonium moiybdate is prepared in the same manner as in Example 1, by

dissolving .10 parts of molybdenum trioxide of solution contains a -mixture of perdimolybdicin which parts are by acid with some permonomolybdic acid, ammonium nitrate, and nitric acid.

The carroting solutions of the foregoing examples, are applied for carroting by combing or brushing them into the fur while the latter is still attached to the pelts. The pelts are then dried, for instance at temperatures from about 100 F. to 250 F., and the fur is subsequently removed by any conventional means. The resulting fur is uniformly carroted, and retains its felting properties indefinitely during storage.

The first example is especially well suited for commercial use. It is possible, as will beappreciated, to efiect the oxidation of molybdic acid by other means than that described and furthermore a solution of a permolybdic acid may be prepared by steps other than those mentioned.

I have mentioned nitric acid as the compound used to acidify my aqueous solution of permolybdic acid, but have found that any strong mineral acid, such as sulphuric or hydrochloric acid will sufiice. Preferably a. volatile mineral acid is used, to avoid possible deleterious effects upon the fur after carroting is complete, and acids which have no tendency to reduce the permolybdates or the oxidizing agents used in' their preparation are preferred. I have specifically mentioned nitric acid for it is relatively cheap and can be easily obtained. In some fur treatment, however, as where a white felt is desired, the nitric acid should be replaced by an equivalent acid for the reason as is well known that nitric acid will discolor the fur and render it impractical for use where a white felt is desired.

The concentration of the freenitric acid (HNOs) in the foregoing examples is about 4%. While this concentration may vary depending upon the type of fur to be carroted, concentrations in excess of about are generally to be avoided in order to prevent injurious efi'ects upon the fur.

In my carroting solution, the permolybdate radical or the molybdenum complex resulting from its reduction in addition to acting as an oxidizing agent also combines with the hydrolytic products of the fiber proteins and protects the fiber from injury resulting from excessive hydrolysis and oxidation. It, therefore, substantially replaces the function of the mercury compounds in the mercury carroting solutions previously used. The carroting effects produced by my solution can be had, therefore, without the danger of mercurial poisoning and obviates the diificulty present in the use of the mercury solutions.

I have found that the concentrations of the permolybdate radicals present in the solution can vary over a substantially wide range, and that definite carroting eflects were obtained with the concentration of permolybdate radical as low as 0.1%. The best results were obtained, however, when the concentration of permolybdate radicals in the solution was within the range from 1 to 10%. The upper concentration limit at which it would be practical to use the permolybdate in solution as a carroting agent would be governed by the cost of the molybdenum salts relative to the valve of the fur to be treated.

It is not necessary to use an acid solution, for I have also prepared a substantially neutral solution of sodium permolybdate by using a solution of sodium molybdate and oxidizing it to a permolybdate. Such a solution used alone or in combination with sodium or ammonium salts of sulphuric, nitric, or hydrochloric acid gave a.

definite'carroting effect, although not as effective as the acid solutions. Such solutions may be prepared for instance by reducing the quantity of nitric acid specified in the foregoing examples sufficient to yield a neutral carroting solution.

Another form in which I have used the per-- molybdate radical was realized by dissolving molybdenum trioxide in an excess of ammonium hydroxide and oxidizing the molybdate to the permolybdate form. Such solutions result if the nitric acid in the foregoing examples is omitted. The alkaline solution of permolybdate alone or modified by the addition of other salts gave definite carroting effects.

The application of my carroting solution to the fur may be carried out in general in the usual manner, which comprises brushing the solution into the fur while the latter is still on the skin.

compounds of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdic acid.

2. A composition of matter for carroting fur or the like comprising an aqueous solution containing, as a carroting adjuvant, a mineral acid salt of the class consisting of alkali metal and ammonium salts, and a permolybdate, said solution being substantially free from other oxygenliberating agents of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdate.

3. A composition of matter for carroting fur or the like comprising an aqueous solution containing a strong, volatile, nonreducing mineral acid, and a permolybdic acid, said solution be-. ing substantially free from other oxygen-liberating agents of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdic acid.

4. A composition of matter for carroting fur or the like comprising an aqueous solution containing a borate of the class consisting of boric acid and its salts, and a permolybdate, said solution being substantially free from other oxygenliberating agents of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdate.

5. A process for carroting 111 or the like to render it suitable for felting comprising treating the fur with a solution containing a permolybdate radical, said solution' being substantially free from other oxygen-liberating compounds of the'group consisting of peroxide and peroxideliberating compounds which are less stable than said permolybdate radical; and subsequently drying the fur. Y

6. A process for carroting fur or the like to render it suitable for felting, comprising treating the fur with a solution comprising a mineral acid and a permolybdic acid, said solution being substantially free from other oxygen-liberating compounds of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdic acid; and subsequently drying the fur.

7. A process for carroting fur or the like to render it suitable for felting, comprising treating the fur withv a substantially neutral solution containing a permolybdate, said solution being substantially free from other oxygen-liberating agents of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybclate; and subsequently drying the fur.

8. The herein described process of preparing fur or the like for felting which comprises treating the far with an aqueous alkaline solution containing salts of a permolybdic acid, said solution being substantially free from other oxygenliberating compounds of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdic acid salt and subsequently drying the fur.

9. The herein described process of preparing fur or the like for felting, which comprises treat-' ing the fur with an aqueous solution containing as a carroting adjuvant, a mineral acid salt of the class consisting of alkali metal and ammonium salts, and a permolybdate, said solution being substantially free from other oxygen-liberating agents or the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdate; and subsequently drying the fur.

10. A process for carroting fur or the like to render it suitable for felting, comprising treating the fur with a solution containing a strong, nonreducing volatile mineral acid and a permolybdic acid, said solution being substantially free from pounds which are less stable than said permolybdic acid; and subsequently drying the fur.

11. A process for carroting fur or the like to render it suitable for felting, comprising treating the fur with an aqueous solution containing. a

borate of the class consisting of boric acid and its salts, and a permolybdate, said solution being substantially free from other oxygen-liberating agents of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdate; and subsequently drying the fur.

12. A process for carroting fur or the like to render it suitable for felting comprising treating the fur with an aqueous solution containing at least 0.1% of a permolybdate radical, said solution being substantially free from other oxygenliberating agents of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdate radical; and subsequently drying the fur.

13. A process for carroting fur or the like to render it suitable for felting comprising treating the fur with an aqueous solution containing from about 1 to about 10% of a permolybdate radical. said solution being substantially free from other oxygen-liberating agents of the group consisting of peroxide and peroxide-liberating compounds which are less stable than said permolybdate radical; and subsequently drying the fur.

JACOB DOLID.

. CERTIFICATE OF CORRECTION. Patent No. 2,2h2,668. May 20, 191p. JACOBDOLID.

It is hereby certifiedthat error appears in the printed specification 'of the above numbered patent requiring correction as follows: Page 5, first oolumn; line 68, for the word "valve" read --va1ue--; page 11., first column,

line 26, claim 9, for "agents or" read -agents of--; and that the said Letters Patent shouldbe read. with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 29th day of July, A. D. 19141.

Henry Van Arsdale, '(Seal) Acting Commissioner of Patents. 

